Electrode Wheel Wiper for EUV Gas Discharge Sources
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Solution Overview
Problem
High rotational frequencies in gas discharge sources lead to increased liquid metal film thickness and droplet formation on electrode wheels, causing short circuits and requiring frequent operational parameter adjustments, limiting the power output and stability of EUV radiation sources.
Innovation Solution
An electrode device with a wiper unit that inhibits the migration of liquid material from the side surfaces to the outer circumferential surface, allowing for controlled film thickness and distribution, enabling higher rotational speeds and stable operation by forming a gap between the outer surface and the wiping edge of the wiper unit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the rotational frequency of the electrode wheels is increased to achieve higher power output, then the repetition rate of discharge increases, but the liquid metal film thickness increases due to higher centrifugal forces, causing droplet formation and short circuits
Solution Approach 1:
The wiper unit extracts and removes the harmful centrifugal force effect by actively scraping the liquid metal film from the electrode wheel surface. This extraction mechanism prevents the film thickness from increasing with rotational frequency, thereby eliminating droplet formation while allowing the electrode wheels to rotate at higher speeds for increased power output
Solution Approach 2:
The wiper unit acts as an intermediary component between the liquid metal film and the electrode wheel surface. It mediates the interaction by controlling the film thickness through mechanical contact, preventing direct harmful effects of centrifugal force on the film stability while enabling higher rotational frequencies
2Productivity
If the rotational speed is increased to achieve higher discharge repetition rate, then the productivity increases, but the liquid metal film becomes unstable and forms droplets, requiring frequent parameter adjustments
Solution Approach 1:
The wiper unit enables the system to self-regulate the liquid metal film thickness automatically during rotation. By continuously scraping the film, the wiper creates a self-stabilizing mechanism that maintains consistent film thickness without requiring external intervention or frequent parameter adjustments, even at high rotational speeds
Solution Approach 2:
The invention changes the operational parameters by introducing a mechanical constraint (wiper contact) that decouples the relationship between rotational speed and film thickness. This parameter change allows the system to operate at higher speeds without the proportional increase in film thickness that would otherwise occur, stabilizing operation across a wider speed range
3Quantity of substance
If the liquid metal film thickness increases at high rotational frequencies, then more material is available for discharge, but droplet formation occurs causing short circuits and lamp failure
Solution Approach 1:
The wiper unit converts the harmful effect of centrifugal force into a beneficial mechanism. Instead of allowing centrifugal force to create unstable thick films and droplets, the wiper utilizes the rotational motion to maintain continuous contact between the wiper and electrode surface, ensuring uniform film thickness and preventing droplet formation while still providing sufficient liquid metal for discharge
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The wiper unit allows for higher rotational speeds and increased pulse frequencies without droplet formation, maintaining a stable liquid film thickness, thereby enhancing the power output and stability of the gas discharge source.
Implementation Method 1
the film thickness of the liquid metal film on the rotating electrode increases with increasing rotational frequency due to the higher centrifugal forces
Data Source
Figure 1
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AI summary
The present invention relates to an electrode device for gas discharge sources, a gas discharge source comprising such an electrode device and to a method of operating the gas discharge source. The electrode device comprises an electrode wheel (1) rotatable around a rotational axis (3) and a wiper unit (11) arranged to limit the thickness of a liquid material film applied to at least a portion of an outer circumferential surface (18) of the electrode wheel (1) during rotation of said electrode wheel (1). The wiper unit (11) is arranged and designed to form a gap (17) between the outer circumferential surface (18) and a wiping edge (19) of the wiper unit (11) and to inhibit or at least reduce a migration of liquid material from side surfaces to the outer circumferential surface (18) of the electrode wheel (1) during rotation. With the proposed electrode device the electrode wheel (1) can be rotated at higher rotational speeds without the formation of droplets resulting in a higher output power and pulse frequency of a gas discharge source having such an electrode device.